Due to recent hard use conditions, lubricant base oils and grease base oils which are used in lubricant compositions and grease compositions such as an engine oil, a gear oil, and a refrigerating machine oil have been required to have enhanced durabilities such as thermal stability, chemical stability, anti-wear properties, and fatigue resistance. Further, energy saving, low-temperature fluidity, low volatility in a high-temperature range, and so forth have also been required. In this respect, the chemical stability includes oxidation stability, hydrolysis stability, oxidation-hydrolysis stability, and the like.
International Publication No. WO2008/117657 describes a refrigerating machine oil characterized by containing an ester of a polyhydric alcohol and fatty acids in which a proportion of branched fatty acids having 10 to 13 carbon atoms is 50 mol % or more.
Published Japanese Translation of PCT International Application No. Hei 5-505806 states that an ester of a C10 to C15 branched aliphatic carboxylic acid containing on average more than one branch per molecule in which no more than 20% of the branching is on the 2 carbon, and an aliphatic alcohol having at least three hydroxyl groups is useful for cutting fluids, hydraulic fluids, and the like.
However, these literatures do not desclose or suggest the characteristics such as low-temperature fluidity, oxidation stability, and low volatility required for lubricant base oils and grease base oils.